1. Field of the Invention
The present invention relates to a method of fabricating a pipe for adsorbing fuel evaporation gas for automobiles.
2. Background of the Related Art
Existing exhaust gas regulation is applied to both exhaust gas released from a tail pipe and evaporation gas (e.g. volatile organic compound: VOC) generated from an automobile.
Typically, problems associated with the exhaust gas are addressed by an engine or post-treatment technology, but problems associated with evaporation gas are difficult to cope with and address as they are involved in the entire structure of the automobile.
Such evaporation gas becomes a main source of the formation of optical smog and has ozone for its main ingredient. Evaporation gas regulation is largely divided into non-fuel regulation and fuel regulation.
The non-fuel regulation is designed to regulate evaporation gas released from an automobile besides a fuel supply system, and the fuel regulation is designed to regulate evaporation gas generated from the fuel supply system. Particularly, in case of the fuel regulation of evaporation gas regulation, it is difficult to satisfy a regulation level of the evaporation gas.
For the fuel regulation, almost all of the evaporation gases are generated in such a fashion that when an automobile engine is stopped, evaporation gas is generated from a fuel tank and flows backwards to an intake air supply system from which air is supplied so as to be discharged to the outside of the automobile. That is, the evaporation gas sequentially flows out via the fuel tank, the engine and the intake air supply system. Also, as another discharge path of the evaporation gas, the evaporation gas flows out from the engine to the intake air supply system so as to be discharged to the outside.
Since such evaporation gas occupies more than 50% of fuel evaporation gas from the automobiles, the collection of the evaporation gas flowing out from the intake air supply system is the easiest strategy for complying with the evaporation gas regulation.
FIG. 3 is a graph illustrating comparisons between an intake air supply system and a general exhaust gas regulation system in terms of the amount of hydrogen carbide (HC) emitted from the intake air supply system and the general exhaust gas regulation system according to the size of automobiles. As shown in a graph of FIG. 3, it can be seen that as the size of vehicles increases, the amount of hydrogen carbide (HC) released from the intake air supply system also increases. Thus, it is necessary that hydrogen carbide (HC) released from the intake air supply system should be removed.
Methods of removing the evaporation gas are largely divided into two cases: a first method of basically suppressing the generation of the evaporation gas, and a second method of removing or adsorbing the evaporation gas which has been released from the intake air supply system.
The first method is to basically suppress the evaporation gas to be generated in consideration of the entire system of the automobiles such as a fuel system (connection portion and fuel tank), an engine system, etc. However, it is difficult for the first method to cope with the evaporation gas regulation as the entire system must be taken into consideration in terms of cost and method.
The second method, i.e., a post-treatment method, is to allow the automobile to be equipped with a component for removing or adsorbing the evaporation gas released from the intake air supply system since the amount of the evaporation gas emitted from the intake air supply system also increases as the displacement of the engine increases.
Specifically, the second method is one for appropriately coping with the evaporation gas regulation in which the evaporation gas from the intake air supply system that occupies around 50% of the total emission amount (in case of large vehicles) of the evaporation gas is effectively eliminated or adsorbed so that the release of the evaporation gas from a part of the vehicle can be efficiently suppressed. Thus, a hydrogen carbide (HC) adsorbent is conventionally installed at the intake air supply system side to cope with the evaporation gas regulation.
To this end, there has been proposed various evaporation gas adsorbing methods. As one method among them, activated carbon is installed at the intake air supply system. But such evaporation gas adsorbing method can have problems in that the back pressure of the exhaust gas increases and that the installed activated carbon is apt to be broken due to vibration occurring during operation of the vehicle, which may adversely affect the engine.
As another evaporation gas adsorbing method, the intake air supply system is equipped with an activated carbon sheet fabricated by mixing pulp and activated carbon and compressing the resultant mixture.
Problems involved with the activated carbon sheet include that the back pressure varies depending on its installation method and position, and the activated carbon granules compressed against the surface of the sheet are broken away due to vibration during vehicle operation, which has an adverse influence on the engine. In addition, since the activated carbon sheet is formed in a flat sheet shape, in the case where it is installed inside an air cleaner or a pipe, sheet-securing means is required to support the activated carbon sheet while exerting a certain force thereto.
Furthermore, the back pressure increases at the activated carbon, but the rolled-type sheet with easy installation needs a linear pipe to be mounted inside the intake air supply system and requires a separate structure which is capable of supplying the sheet with a certain force when being installed.